Food grade colored fluids for printing on edible substrates

ABSTRACT

Food grade colored fluids which include food grade dyes and food grade glycols are provided. Also provided are methods for applying the food grade colored fluids directed to the surface of an edible substrate, and edible substrates having the food grade colored fluids applied to a surface thereof. The food grade colored fluids may optionally include glycerine and water. In one embodiment, the food grade glycol makes up at least about 25 wt. % of the colored fluid and water makes up no more than about 35 wt. % of the colored fluid.

BACKGROUND

Ink jet printing is a printing application with the potential for wideuse in decorating the surfaces of food items. However, in order to besuitable for use on foods, ink formulations should be food gradeformulations, should be compatible with the food surfaces onto whichthey will be applied, and should have properties (e.g., viscosities,surface tensions, smear resistance, solubilities, drying times) thatmake them suitable for use with ink jet printers. Few presentlyavailable inks meet all of these limitations. For example, many ink jetink formulations include compounds that cause deleterious health effectswhen ingested by humans. Other ink formulations have high watercontents, resulting in viscosities that are too low to permit the inksto be successfully jetted onto an edible surface. Still other ink jetink formulations are incapable of being printed directly onto a foodsubstrate without smearing or image bleed. One solution that has beenused to deal with this latter problem is to print a decoration onto anedible paper, such as rice paper, and then to apply the decorated paperto a food item. Unfortunately, this process involves multiple processingsteps and is not well suited for use with food items of all shapes andsizes. Thus, a need exists for a food grade coloring formulation thatcan be printed directly onto the surfaces of a variety of food items toproduce a high quality image using ink jet printing technology.

SUMMARY

Food grade colored fluids for use in printing on edible substrates,methods for applying the food grade colored fluids directly to ediblesubstrates, and edible substrates having the colored fluids appliedthereto are provided. The food grade colored fluids are typically madefrom food grade dyes and glycols and optionally water and/or glycerine.The food grade colored fluids have characteristics that render themsuitable for printing directly onto the surfaces of a variety of ediblesubstrates. In particular, the food grade colored fluids may be suitablefor printing with ink jet printers, including piezoelectric ink jetprinters. As used herein, the phrase “food grade” means that up tospecified amounts of the particular compound can be ingested by a humanwithout generally causing deleterious health effects. Examples of foodgrade compounds include those compounds “generally recognized as safe”(“GRAS”) by the United States Food and Drug Administration (“FDA”) andcolorants approved by the FDA for use in foods for human consumption. Inparticular, food safe compounds include those compounds listed asapproved under 21 C.F.R. §§ 73, 74, 172, 182 and 184.

The colored fluids may contain substantial amounts of food gradeglycols, such as 1,2-propanediol. In some embodiments, the coloredfluids include at least about 10 weight percent (wt. %) food gradeglycol. This includes embodiments where the colored fluids include atleast about 25 wt. % food grade glycol and further includes embodimentswhere the colored fluids include at least about 40 wt. % food gradeglycol. In addition to the food grade glycols, the colored fluids mayoptionally include water, glycerine or a mixture of water and glycerine.In one typical embodiment, the food grade glycol and any water orglycerine present account for at least about 90 wt. % of the food gradecolored fluid.

The food grade colored fluids may be prepared with a low water content.For example, in some embodiments the food grade colored fluids maycontain no more than about 35 wt. % water. This includes embodimentswhere the colored fluids contain no more than about 20 wt. % water,further includes embodiments where the colored fluids contain no morethan about 5 wt. % water. The food grade colored fluids may be free ofor substantially free of water, e.g. having a water content of no morethan about 1 wt. %. In these compositions, any water present may be duesolely or partially to water absorbed from the air under humidconditions and/or water introduced as an impurity or minor component ofone of the dyes or solvents that make up the colored fluids. It isadvantageous to limit the amount of water present in the colored fluidsbecause a high water content tends to decrease the viscosity of thefluids, rendering them less suitable for use in some printingapplications, such as ink jet printing applications where elevatedjetting temperatures are used.

Although not a necessary ingredient, glycerine is a useful co-solventbecause many of the food grade dyes used in the colored fluids exhibithigh solubility in glycerine. Typically, when glycerine is present, itmakes up at least about 3 wt. % of the colored fluid. This includesembodiments where glycerine makes up at least about 10 wt. % of thecolored fluid, further includes embodiments where glycerine makes up atleast about 20 wt. % of the colored fluid, and still further includesembodiments where glycerine makes up at least about 30 wt. % of thecolored fluid. The amount of glycerine present, if any, will depend on avariety of factors, including the extent to which the food grade dyesare soluble in the food grade glycols. Thus, some of the colored fluidsmay contain a relatively small amount of glycerine (e.g. about 2 to 10wt. %) and others may contain a larger amount of glycerine (e.g. about30 to 45 wt. %). In still other embodiments, glycerine is present inintermediate quantities (e.g. about 12 to 18 wt. %).

The food grade dyes used to produce the colored fluids may includesynthetic dyes, natural dyes, or combinations thereof. As used herein,the term “dye” denotes dyes which are soluble in water and/or in theother cosolvents, which contain substantial amounts of glycols and/orglycerine, employed in the present colored fluids. In some embodiments,the colored fluids may be substantially free of insoluble materials.Suitable synthetic dyes for use in the present coloring fluids includefood grade FD&C dyes, such as FD&C Red #3, FD&C Red #40, FD&C Yellow #5,FD&C Yellow #6, FD&C Blue #1, and FD&C Green #3. Suitable natural dyesinclude turmeric oleoresins, cochineal extracts, gardenia extracts, andnatural colors derived from vegetable juices. Other specific examples ofsuitable natural dyes include, but are not limited to, beet extract,grape skin extract, and chlorophyll containing extracts (e.g. nettleextract, alfalfa extract and spinach extract). To achieve a desiredcolor tint or shade, the colored liquids may include mixtures of morethan one synthetic and/or natural food grade dye. In a typicalembodiment, the colored fluids contain about 0.1 to 10 wt. % food gradedye on a dissolved solids basis (dsb). This includes embodiments wherethe colored fluids contain about 0.5 to 7.5 wt. % (dsb) food grade dyeand further includes embodiments where the colored fluids contain about0.5 to 5 wt. % (dsb) food grade dyes.

Because they are intended for use on edible substrates, the coloredfluids are desirably made with high purity food grade dyes. For example,the food grade dyes used in the colored fluids may be at least about 85wt. % pure. That is, the dyes may contain no more than about 15 wt. %contaminants and impurities, including moisture. In some instances, thefood grade dyes are at least about 87 wt. % pure. Alternatively, thepurity of the dyes may be analyzed on a strictly dry weight basis, inwhich case the food grade dyes are desirably at least about 92 wt. %pure. In some embodiments the food grade dyes are at least about 95 wt.% pure when analyzed on a dry weight basis. This includes embodimentswhere the food grade dyes are at least about 98 wt. % pure when analyzedon a dry weight basis.

Inorganic salts, such as sodium chloride and sodium sulfate, areexamples of common impurities found in food grade dyes, such as foodgrade FD&C dyes. Unfortunately, fluids having elevated salt contents maybe corrosive to printer parts and lead to shorter printer lifetimes.Therefore, it is typically advantageous to use food grade dyes having alow inorganic salt content, or at least a low chloride and/or sulfateion content, in the preparation of the colored fluids. In some exemplaryembodiments, the colored fluids contain one or more synthetic food gradedyes having an inorganic salt content, and more specifically in someinstances a chloride and/or sulfate ion content, of no more than about0.5 wt. %. This includes embodiments where the colored fluids containone or more synthetic food grade dyes having an inorganic salt content,or at least a chloride and/or sulfate ion content, of no more than about0.2 wt. % desirably no more than about 0.1 wt. %. The salt (e.g.chloride and or sulfate ion) impurity level in the synthetic food gradewill desirably be no more than about 1000 ppm. In some embodiments, theimpurity level will be no more than about 500 ppm and in still otherembodiments the impurity level will be no more than about 100 ppm.

In addition to food grade dyes and glycols and any optional glycerineand/or water, the food grade colored fluids may contain various foodgrade additives, such as surface tension modifiers, thickening agents,antioxidants, preservatives, buffering agents, and antimicrobial agents.These additional additives are typically present in small quantities,for example, no more than about 10 wt. % and desirably no more thanabout 5 wt. %. Lower alcohols (i.e. alcohols having one to six carbonatoms), such as isopropanol, ethanol, n-butyl alcohol, and i-butylalcohol, or mixtures thereof are examples of additives that might bepresent in limited amounts in the colored fluids. The lower alcohols maybe used as surface tension modifiers and will generally be present inamounts of no more than about 10 wt. %. This includes embodiments wherethe lower alcohols are present in amounts of no more than about 5 wt. %and further includes embodiments where the lower alcohols are present inamounts of no more than about 0.5 wt. %.

The colored fluids desirably have properties that render them suitablefor use as printing inks in various types of printers, including ink jetprinters which utilize piezoelectric printheads. Viscosity is oneproperty of the colored fluids that may be controlled to produce fluidssuitable for ink jet printing. It is generally desirable for the coloredfluids to have a viscosity of about 8 to 14 centipoise (cps) at thejetting temperature at which the printing is to take place. In someembodiments, the colored fluids have a viscosity of 8 to 12 cps at thedesired jetting temperature. Typical jetting temperatures may range fromroom temperature, about 25° C., to elevated temperatures of at leastabout 80° C. or even higher. Typical elevated jetting temperatures mayrange from about 50 to 70° C. For example, a colored fluid may have aviscosity of about 8 to 14 cps at a jetting temperature of 60° C.Alternatively, a colored fluid may have a viscosity of about 8 to 14 cpsat a jetting temperature of 25° C.

The colored fluids presented herein desirably, but not necessarily,exhibit Newtonian viscosities, that is, viscosities that do not changewith shear rate. In particular, the colored fluids may exhibit aBrookfield viscosity that changes by no more than about 2 cps with ashear rate increase from about 15 to 45 rpm when measured at atemperature selected from a temperature in the range of 20 to 70° C.(e.g., 60° C.). In some embodiments, the colored fluids exhibit aBrookfield viscosity that changes by no more than about 1 cps and instill other embodiments, the colored fluids exhibit a Brookfieldviscosity that changes by no more than about 0.5 cps with a shear rateincrease from about 15 to 45 rpm when measured at a temperature selectedfrom a temperature in the range of 20 to 70° C. (e.g., 60° C.).

The colored fluids will typically have surface tensions of about 20 to60 dynes per centimeter (cm) at 25° C. This includes embodiments wherethe colored fluids have surface tensions of 35 to 50 dynes per cm at 25°C.

To prevent clogging of ink jet printer nozzles it is advantageous toprovide colored fluids having reduced particle content. Particle contentmay be characterized by the silt density index (SDI) of the fluid. SDIvalues provide a measure of particle content that relates the rate ofmembrane clogging to the quantity of particulate matter present in afluid. SDI values may be measured as follows: two aliquots of equalvolume of the fluid to be tested are poured sequentially into a filterand the time required for each aliquot to pass through the filter ismeasured. The SDI is provided by the ratio of the time it takes thefirst aliquot to pass through the filter to the time it takes the secondaliquot to pass through the filter. A higher SDI value indicates a fluidhaving a lower particle content. A fluid that has no buildup on thefilter, and therefore very little particle content, will have an SDIvalue of 1. The food grade colored fluids provided herein include, butare not limited to, fluids having an SDI of at least about 0.5. Incertain embodiments the colored fluids have an SDI of at least about0.75. This includes embodiments where the colored fluids have an SDI ofat least about 0.9.

Unless otherwise noted, an SDI value for a given liquid sample may bemeasured at any arbitrary time after the sample is prepared withoutrequiring any particular set of processing conditions to have beenpreformed prior to the measurement. In some cases, see Example 1 below,a Heat Test SDI value is quoted. As used herein, a Heat Test SDI valueis measured after heat-aging the sample for at least 11 days at atemperature of at least 70° C. according to the procedure described inExample 1.

The food grade colored fluids may also have a relatively low specificgravity. In a typical embodiment, the food grade colored fluids may havea specific gravity of no more than 1.15. This includes embodiments wherethe colored fluids have a specific gravity of no more than 1.13 andfurther includes embodiments where the colored fluids have a specificgravity of no more than 1.10.

Once prepared, the present colored fluids may be printed directly ontothe surfaces of a variety of edible substrates using conventionalprinting equipment, such as ink jet printers. The surfaces onto whichthe fluids are printed are desirably porous in order to facilitateabsorption of the dye by the surface. Suitable edible substratesinclude, but are not limited to, crackers, chewing gum, biscuits,cereal, taco shells, granola bars, rice cakes, cookies, pie crusts,waffles, cakes, including snack cakes, marshmallows, candies, pasta andvarious bread products, such as toast, buns, bagels and tortillas.

DETAILED DESCRIPTION

Food grade colored fluids are provided. The food grade colored fluids,which contain at least one food grade dye and a food grade glycol, suchas 1,2-propanediol, are useful for printing directly onto the surfacesof various edible substrates. As used herein, “food grade” means that upto specified amounts of the particular compounds can be ingested by ahuman without generally causing deleterious health effects. Therefore,in order to meet the standard of a “food grade” colored fluid, thecolored fluid should be free or substantially free of compounds thatgenerally cause deleterious health effects when ingested by a human.When such compounds are present, e.g. in trace amounts throughcontamination, those compounds should be present in amounts below thosethat would result in the deleterious health effects.

The food grade colored fluids are well-suited for use with a variety ofink piezo printheads. Examples of manufacturers from which theprintheads may be obtained include Spectra, Xaar, Hitachi and PicoJet.

Edible substrates onto which the colored fluids have been applied arealso provided. Examples of edible substrates onto which the food gradecolored fluids may be printed include, but are not limited to, crackers,chewing gum, biscuits, cereal, taco shells, granola bars, rice cakes,cookies, pie crusts, waffles, cakes, including snack cakes,marshmallows, candies, pasta, and various bread products such as toast,buns, bagels, and tortillas. This surface of the edible substrate ontowhich the food grade colored fluids are applied is desirably a poroussurface which facilitates the absorption of the food grade coloredfluids by the surface, hastening drying. As used herein, the term“porous surface” is intended to include any surface having sufficientporosity to allow the food grade colored fluids to be at least partiallyabsorbed. The food grade colored fluids may also be applied to nonporousedible surfaces, however, the application of the colored fluids to suchsurfaces may require a drying step after the colored fluid has beenapplied.

The food grade glycol acts as a solvent and may account for a large partof the colored fluid. For example, the food grade glycol may account forat least about 25 wt. % of the colored fluid. This includes embodimentswhere the food grade glycol accounts for at least about 40 wt. % of thecolored fluid, further includes embodiments where the food grade glycolaccounts for at least about 70 wt. % of the colored fluid, and stillfurther includes embodiments where the food grade glycol accounts for atleast about 85 wt. % of the colored fluid. Optionally, glycerine, water,or a mixture of glycerine and water, may be used as co-solvents alongwith the food grade glycol. However, in many colored fluids the amountof water present in the colored fluids may be limited in order tomaintain a higher viscosity. For some applications, higher viscositiesmay be advantageous because they can render the colored fluids suitablefor ink jet printing at elevated jetting temperatures.

Glycerine is a good co-solvent of choice because of its relatively lowvolatility and its presence may assist in solubilizing some of the foodgrade dyes. As such, glycerine helps prevent the food grade dyes fromsolidifying out of solution, crusting onto and clogging jetting nozzles.When glycerine is used as a co-solvent, it is typically present in anamount of at least about 3 wt. %. This includes embodiments whereglycerine is present in an amount of at least 10 wt. %, further includesembodiments where glycerine is present in an amount at least about 20wt. %, still further includes embodiments where the glycerine is presentin an amount of at least 30 wt. %, and even further includes embodimentswhere the glycerine is present in an amount of at least about 45 wt. %.In one exemplary embodiment, the food grade colored fluids contain atleast about 70 wt. % 1,2-propanediol, glycerine or a mixture thereof. Inanother exemplary embodiment, the food grade colored fluids containabout 25 to 95 wt. % 1,2-propanediol, about 3 to 40 wt. % glycerine andno more than about 35 wt. % water.

The food grade dyes used to produce the colored fluids may be syntheticdyes, natural dyes or a mixture of synthetic and natural dyes. The foodgrade dyes may include any dyes which are soluble in at least one of1,2-propanediol, glycerine, water, or mixtures thereof. In someembodiments, it is desirable that the food grade colored fluids be freeof insoluble coloring agents such as a pigments or lakes. Examples ofsuitable dyes include, but are not limited to, synthetic dyes, such asFD&C dyes (e.g., FD&C Red #3, FD&C Red #40, FD&C Yellow #5, FD&C Yellow#6, FD&C Blue #1, and/or FD&C Green #3).

Examples of suitable natural dyes include, but are not limited to,turmeric oleoresins, cochineal extracts including carminic acid,gardenia extracts, beet extracts, and other natural colors derived fromvegetable juices, and chlorophyll-containing extracts, such as nettleextract, alfalfa extract and spinach extract. Anthocyanins are anotherclass of food grade dyes that may be used in the colored fluids. Theanthocyanins may be derived from a variety of plant sources, includingfruit juices, elderberries, black currants, chokeberries, vegetablejuices, black carrots, red cabbage, grapes and grape skins, and sweetpotatoes. Although the relative amount of the food grade dyes used inthe food grade colored fluids may vary depending on the desired color,shade and intensity, the food grade colored fluids will typicallycontain about 0.1 to 10 wt. % (dsb) food grade dye. This includesembodiments where the colored fluids contain about 0.5 to 7.5 wt. %(dsb), and further includes embodiments where the colored fluids containabout 0.5 to 5 wt. % (dsb) food grade dye.

The food grade dyes used to produce the colored fluids are desirablyhigh purity food grade dyes. In some instances, the food grade dyes maypossess purities of at least 85 wt. %, where any water present in thedye is included as an impurity. This includes embodiments where the foodgrade dyes are at least 87 wt. % pure. When the purity of the dye isanalyzed strictly on a dry weight basis, the food grade dyes desirablyhave a purity of at least 92 wt. %. This includes embodiments where thefood grade dyes have a purity of at least about 95 wt. % and stillfurther includes embodiments where the food grade dyes have a purity ofat least about 98 wt. % when analyzed on a dry weight basis. Typicalimpurities found in commercially available food grade dyes, includingmany FD&C dyes, may include minerals, such as calcium, metals, such asiron, salts such as sodium chloride and sodium sulfate, and smallamounts of water. Typically, the impurity level of minerals and metalsin the food grade dyes will be no more than about 50 ppm. However, insome instances, the impurity levels of these components will be muchless. For example, in some of the food grade dyes, the impurity level ofcalcium will be no more than about 10 ppm and desirably no more thanabout 5 ppm. Similarly, in many suitable food grade dyes, the impuritylevel of iron will be no more than about 10 ppm and desirably no morethan about 4 ppm. Water will typically be present as an impurity in thefood grade dyes in an amount of no more than about 5 wt. %. Thisincludes embodiments where water is present as an impurity in an amountof no more than about 2 wt. % and still further includes embodimentswhere water is present as an impurity in the food grade dyes in anamount of no more than about 1 wt. %.

Some inorganic salts are particularly undesirable impurities becausethese salts tend to corrode printer parts, including printing headswhich reduces the lifetime of the printers used to apply the dyes.Therefore, for certain applications it may be advantageous to reduce thelevel of inorganic salt impurities in the food grade dyes. When amixture of food grade dyes is utilized, a reduction in inorganic saltcontent and corrosiveness may be achieved provided at least one of thefood grade dyes, and in particular at least one FD&C food grade dye, hasa low inorganic salt content. It such embodiments, it may be desirablefor any food grade dyes that do not have a low salt content to bepresent in amounts of no more than about 1 wt. % or in amounts of nomore than about 0.6 wt. %. In some colored fluids containing a mixtureof food grade dyes, all of the food grade dyes in the mixture have a lowinorganic salt content. In some embodiments the food grade coloredfluids provided herein are made with one or more synthetic food gradedyes having an inorganic salt impurity level of no more than about 0.5wt. %. This includes embodiments where one or more of the synthetic foodgrade dyes has an inorganic salt content of no more than about 0.2 wt. %and further includes embodiments where one or more of the synthetic foodgrade dyes has an inorganic salt content of no more than about 0.1 wt.%. Alternatively stated, in some instances, the inorganic salt impuritylevel in one or more of the synthetic dyes will be no more than about1,000 ppm. In other instances, the inorganic salt impurity level in oneor more of the synthetic food grade dyes will be no more than about 500ppm and in still other instances the inorganic salt impurity level inone or more of the synthetic dyes will be no more than about 100 ppm.Two typical corrosive inorganic salts found in commercially availabledyes, including synthetic dyes, such as FD&C food grade dyes arechlorides, which usually take the form of sodium chloride, and sulfates,which typically take the form of sodium sulfates. In some instances itmay be possible for the colored fluids to include higher levels ofcertain less corrosive salts provided the levels of chlorides and/orsulfates in the dyes remains low. Thus, in certain embodiments, theinorganic salt content and impurity limits cited above may beinterpreted to refer specifically to chloride and/or sulfate ion contentin the colored fluids. Table 1 below shows exemplary formulations fortwo high-purity, low-salt food grade dyes that my be used to produce thefood grade colored fluids. Both dyes shown in Table 1 are available fromSensient Colors Inc., St. Louis, Mo.

TABLE 1 Low Inorganic Salt Food Grade Dyes Low Salt FD&C Yellow Low SaltFD&C Blue Calcium 5 ppm — Iron 4 ppm — Water — 3.6 wt. % NaCl 25 ppm 2ppm Na₂SO₄ 51 ppm 34 ppm Dye 95 wt. % 95 wt. %

In addition to the food grade dyes and glycols and any optionalglycerine and/or water co-solvents, the food grade colored fluids maycontain other food grade additives such as surface tension modifiers,thickening agents, antioxidants, preservatives, buffering agents, andanti-microbial agents. These additional additives will typically bepresent only in small quantities. For example, the additional food gradeadditives may be present in amounts of no more than about 10 wt. %. Thisincludes embodiments where the food grade additives are present inamounts of no more than about 5 wt. % and further includes embodimentswhere the food grade additives are present in amounts of no more thanabout 3 wt. %. The additives may include isopropanol, ethanol, ormixtures thereof as surface tension modifying agents. In a typicalembodiment, a colored fluid may contain no more than about 10 wt. %isopropanol, ethanol, or a mixture thereof and more typically about 1 to5 wt. %. The colored fluids may contain no more than about 3 wt. % loweralcohol and in some embodiments the colored fluids may be substantiallyfree of lower alcohol, such as isopropanol, i.e., contain no more thanabout 0.5 wt. % lower alcohol. Methylparaben, propylparaben or mixturesthereof may be included in the food grade colored fluids aspreservatives. For some applications it is desirable to exclude certainadditives. For example, some food grade colored liquids in accordancewith this disclosure may be free of or substantially free of one or moreof the following additives: glycol ethers, polyol monoethers, urea,tetraalkylammonium cations (e.g. tetramethylammonium cations), alkanolammonium compounds (e.g., monoethanol ammonium compounds,diethylammonium compounds, or triethanol ammonium cations), cationicamide compounds (e.g., protonated formamide), silica, sebacyl chlorides,binding agents and film-forming agents. A food grade colored fluid is“substantially free of” an additional food grade additive if the coloredfluid contains no more than about 0.5 wt. % of the additional food gradeadditive. In some instances, the food grade colored fluid contains nomore than about 0.2 wt. % of a given additive. In still other instancesthe food grade colored fluid contains no more than about 0.1 wt. % of agiven additive. For example, it may be desirable to have food gradecolored fluids which contain no more than about 0.05 wt. % bindingagents and/or film-forming agents, such as polymers, gum arabic,hydrocolloids, xanthum gum, waxes, alginates and polysaccharides.

For ink jet printing applications, it is generally desirable for thecolored fluids to have a viscosity of about 8 to 14 centipoise (cps) atthe jetting temperature at which the printing is to take place. Thisincludes embodiments where the colored fluids have a viscosity of 8 to12 cps at the desired jetting temperature. Some ink jet printers aredesigned to be operated at ambient temperatures (i.e. about 25° C.).Other ink jet printers are designed for operation at elevated print headtemperatures. For example, an ink jet printer may operate at jettingtemperatures ranging from about 50 to 70° C. Therefore, the formulationof the colored fluids, including the ratio of food grade glycol toglycerine and the amount of water present, is desirably controlled toprovide a suitable viscosity for the intended jetting temperature. Forexample, a colored fluid may be tailored to have a viscosity of about 8to 14 cps at a jetting temperature of 60° C. However, the viscosity ofthese colored fluids may be significantly higher at ambienttemperatures. For example, the colored fluids may have viscosities ofabout 35 to 65 cps at 25° C. Alternatively, a colored fluid may betailored to have a viscosity of about 8 to 14 cps at a jettingtemperature of 25° C.

It has been discovered that colored fluids exhibiting Newtonianviscosities, perform favorably as printing inks for edible substrates.Thus, in some embodiments, the colored fluids have Newtonianviscosities. Specifically, the colored fluids may exhibit a Brookfieldviscosity that changes by no more than about 2 cps with a shear rateincrease from about 15 to 45 rpm at 60° C. In some embodiments, thecolored fluids exhibit a Brookfield viscosity that changes by no morethan about 1 cps and in still other embodiments, the colored fluidsexhibit a Brookfield viscosity that changes by no more than about 0.5cps with a shear rate increase from 15 to 45 at 60° C.

The surface tension of the colored fluids may vary over a relativelywide range, provided it is suitable to allow the colored fluids to bejetted through an ink jet printing head and printed onto the surface ofan edible substrate. In some embodiments, the colored fluids will havesurface tensions of about 20 to 60 dynes per cm at 25° C. This includesembodiments where the colored fluids have surface tensions of 35 to 50dynes per cm at 25° C.

The food grade colored liquids desirably have relatively low particlecontents. As such, some of the colored liquids are solutions of one ormore food grade dyes that filterable through a 0.2 μm filter. Onemeasure of the level of particle content may be provided by the siltdensity index of the colored fluids, which is desirably close to 1. Thefood grade colored fluids provided herein include, but are not limitedto, fluids having an SDI of at least about 0.5. In certain embodimentsthe colored fluids have an SDI of at least about 0.75. This includesembodiments where the colored fluids have an SDI of at least about 0.9and still further includes embodiments where the colored fluids have andSDI of at least about 0.95.

Low specific gravity may be advantageous in some applications. In atypical embodiment, the food grade colored fluids may have a specificgravity of no more than 1.13. This includes embodiments where thecolored fluids have a specific gravity of no more than 1.10 (e.g., about1.00 to 1.10).

The pH values of the food grade colored fluids is not critical, howeverit may be advantageous to provide colored fluids with an apparent pH ofat least 4 and desirably at least 5 to prevent the colored fluids fromcorroding printer parts. Generally, the colored fluids include, but arenot limited to, those having an apparent pH in the range of about 4 to9. This includes colored fluids having an apparent pH in the range ofabout 5 to 8. Apparent pH values may be read directly from any suitable,commercially available pH meter. Although these apparent pH values maynot be interpreted as an index of hydrogen ion potential nor used inequilibrium computations, they are reproducible and useful forqualitative purposes.

The following illustrative embodiments are intended to further exemplifythe food grade colored fluids. These embodiments should not beinterpreted as limiting the scope of the colored fluids disclosedherein.

A food grade colored fluid containing a food grade dye, about 25 wt. %of a food grade glycol, which may be 1,2-propanediol, optionallyglycerine and optionally water is provided. In this colored fluid, thefood grade glycol and any optional glycerine and water make up at leastabout 90 wt. % of the colored fluid, and any water present makes up nomore than about 35 wt. % of the colored fluid.

The above-described colored fluid may be further defined by a variety ofadditional ingredients, properties and range limitations to provide anumber of different embodiments of the food grade colored fluids. A fewof these embodiments will now be described in more detail. In oneembodiment of the above-described colored fluid, the food grade glycolmakes up at least about 40 wt. % of the colored fluid. When glycerine ispresent, the colored fluid may contain at least about 3 wt. % glycerine.In applications where it is desirable to limit the amount of waterpresent, water may make up no more than about 20 wt. % of the coloredfluid. In other formulations, the water may account for an even smallerfraction of the colored fluid. For example, any water present may makeup no more than about 1 wt. % of the colored fluid. A specificembodiment of the above-described colored fluid may contain about 0.5 to7.5 wt. % of the food grade dye. The food grade dye in the colored fluidmay be FD&C Red #3, FD&C Red #40, FD&C Yellow #5, FD&C Yellow #6, FD&CBlue #1 or a mixture thereof. The colored fluid may include one or moresynthetic food grade dyes having an inorganic salt content of no morethan about 0.5 wt. %. The colored fluid may also contain a food gradenatural dye instead of or in combination with one or more syntheticdyes. The colored fluid may have one or more the following properties: aviscosity of about 8 to 14 cps at 60° C., a surface tension of about 20to 60 dynes per cm at 25° C., a specific gravity of no more than about1.13, a silt density index of at least about 0.5, and a Brookfieldviscosity at 60° C. that changes by no more than 2 cps over a shear raterange from about 10 to 45 rpm.

A food grade colored fluid containing about 0.1 to 10 wt. % food gradedye, about 25 to 95 wt. % 1,2-propanediol, about 1 to 50 wt. %glycerine, and no more than about 35 wt. % water is provided. Thiscolored fluid has a viscosity of about 8 to 14 cps at 60° C.

A food grade colored fluid containing a food grade dye, a food gradeglycol, optionally glycerine and optionally water is provided. In thiscolored fluid the food grade glycol and any optional glycerine and watermake up at least about 90 wt. % of the colored fluid and any waterpresent makes up no more than about 35 wt. % of the colored fluid. Thecolored fluid is characterized by a Brookfield viscosity at 60° C. thatchanges by no more than 2 cps over a shear rate range from about 10 to45 rpm. In one embodiment, the colored fluid contains at least about 25wt. % 1,2-propanediol as the food grade glycol. The colored fluid mayhave a surface tension of about 35 to 50 dynes per cm at 25° C. and/or aviscosity of about 35 to 65 cps at 25° C.

A food grade colored fluid comprising a food grade dye and at leastabout 25 wt. % 1,2-propanediol is provided. The food grade dye in thecolored fluid has an inorganic salt content of no more than about 0.5wt. %. The food grade colored fluid may optionally include glycerine. Insome embodiments, the colored fluid contains at least about 70 wt. %1,2-propanediol, glycerine or a mixture thereof. The colored fluid mayhave a viscosity of about 35 to 65 cps at 25° C.

A food grade colored fluid comprising a food grade dye and at leastabout 70 wt. % 1,2-propanediol, glycerine or a mixture thereof isprovided. This colored fluid has a viscosity of about 35 to 65 cps at25° C. The amount of 1,2-propanediol in the colored fluid may besubstantial. For example, the colored fluid may contain at least about40 wt. % 1,2-propanediol. This includes embodiments where the coloredfluid contains at least about 85 wt. % 1,2-propanediol. Glycerine may bepresent in the colored fluid in amounts of about 2 to 10 wt. %.Alternatively, glycerine may be present in amounts of about 35 to 45 wt.%. The colored fluid may further include isopropanol, ethanol or amixture thereof. Methylparaben, propylparaben or a mixture thereof mayalso be present in the colored fluid. In applications where a low watercontent is desirable, the colored fluid may contain no more than about20 wt. % water. This includes embodiments where the colored fluidcontains no more than about 1 wt. % water. The colored fluid may containone or more of the following synthetic food grade dyes, FD&C Red #3,FD&C Red #40, FD&C Yellow #5, FD&C Yellow #6, or FD&C Blue #1. Inembodiments where the colored fluid contains one or more synthetic foodgrade dyes, one or more of those dyes may have an inorganic salt contentof no more than about 0.5 wt. %. This includes embodiments wherein atleast one synthetic food grade dye has a chloride content (as sodiumchloride) of no more than about 1000 ppm and a sulfate content (assodium sulfate) of no more than about 1000 ppm. The colored fluid mayalso contain a natural food grade dye. The natural dye may include oneor more the following dyes: a turmeric oleoresin, a cochineal extract,gardenia yellow, gardenia blue, or beet powder. The colored fluid mayhave one or more of the following properties: a viscosity of about 8 to14 cps at 60° C., a surface tension of about 35 to 50 dynes per cm at25° C., a silt density index of at least about 0.5, a specific gravityof no more than about 1.13, or a specific gravity of no more than about1.10.

A method of applying an edible colorant to a surface of an ediblesubstrate, by ink jet printing any one of the above-described food gradecolored fluids directly onto the surface of the edible substrate isprovided. The ink jet printing may take place at a range of jettingtemperatures. For example, the ink jet printing may take place at ajetting temperature of about 25 to 75° C. This includes methods ofprinting where the ink jet printing takes place at a jetting temperatureof about 50 to about 70° C. One or more piezoelectric print heads may beused in the printing process.

An edible substrate having any one of the above-described food gradecolored fluids applied to one or more surfaces thereof is also provided.

EXAMPLES

Exemplary embodiments of the present food grade colored fluids areprovided in the following examples. The following examples are presentedto illustrate the present food grade colored fluid and methods forapplying the colored fluids to edible substrates and to assist one ofordinary skill in making and using the same. The examples are notintended in any way to otherwise limit the scope of the invention.

Instrumentation and Measurements

Examples 1 through 5 below provide examples of various food gradecolored fluids. The formulations (in weight percent) and severalphysical characteristics of the fluids are provided in Tables 2-8. Thephysical characteristics presented in the tables were measured asfollows. Viscosity measurements were obtained using a BrookfieldProgrammable LVDV II⁺ Digital Calculating Viscometer and a Brookfield DVIII Rheometer Model V3.3LV with ULA spindle manufactured by BrookfieldEngineering Laboratories, Inc., Middleboro, Mass. Surface tensionmeasurements were made using the DuNuoy Ring tensiometer method. TheDuNuoy Ring tensiometer (Fisher Model 20 manual DuNuoy Ring Tensiometeror CSC Model 70535) may be obtained from Fisher Scientific or CSCScientific Co., Fairfax, Va. or from companies such as Cole Palmer orVWR. Absorbance measurements were obtained with a Perkin Elmer Lambda 2UV/Visible Spectrometer. Specific gravity was measured with a weight pergallon cup which meets ASTM methods. A weight per gallon cupaccommodates 8.321 grams of water at 77.0 degrees ° F. (25° C.). Theapparent pH values were read directly from an Orion Model 420Aelectronic pH meter with an Orion 91-55 electrode, after calibrating theinstrument with appropriate buffers and immersing the electrode into thecolored fluids.

SDI measurements were obtained using a modified ASTM D4189-82 protocolfor SDI of water. SDI testing is a method that relates the rate ofmembrane plugging or clogging to the quantity of particulate matter inthe fluid. In the modified procedure, designated “Heat Test SDI” in thetables, a stainless steel filter funnel (25 mm, 50 ml bowl capacity) wasplaced over a 250 ml filter flask hooked up to a vacuum and a vacuumgauge. A Pall Versapor® 25 mm, 0.45 μm membrane filter disk was placedin the filter funnel and pre-moistened with a few drops of the fluid tobe tested. The vacuum pressure was set to 23 in. of mercury. The fluidto be tested was heat aged for 11 days at 70° C. Heat-aging is notnecessary to determine the SDI of the colored fluids. SDI may bemeasured substantially immediately after the colored fluids areprepared. In these experiments, the colored fluids were heat-aged inorder to test the shelf life of the fluids. A high SDI index after theaging process indicates that significant particle formation does notoccur and indicates a long shelf life for the fluids.

After heat-aging, twenty ml of the heat-aged fluid to be tested waspoured into the filter funnel and a stopwatch (with a resolution ofhundredths of a second) was used to measure the time required for thefluid to pass through the filter. This time was recorded as “T₁” A 160ml aliquot of the heat-aged fluid to be tested was then poured into thefilter funnel and allowed to pass through the filter. Although the timerequired for this second aliquot to pass through the filter need not berecorded, it is designated “T₂.” Next, a second 20 ml aliquot of theheat-aged liquid to be tested was poured into the filter funnel and thetime required for the fluid to pass through the filter was measured withthe stopwatch. This time was recorded as “T₃.” SDI is then calculated bydividing T₁ by T₃.

Example 1 Preparation of Non-Aqueous Food Grade Colored Fluids

This example describes a method for producing non-aqueous food gradecolored fluids from food grade FD&C dyes, 1,2-propanediol and glycerine.Three illustrative formulations and colors for these formulations areshown in Table 2. The colored fluids were prepared as follows. The1,2-propanediol, glycerine, methylparaben and propylparaben were mixedtogether in a container approved for food use at 50° C. forapproximately 20 minutes. The FD&C dyes were then added while mixing,the heater was turned off, and mixing continued for about one hour. Nextthe isopropanol was added, the mixing continued for another ten minutesand the mixture was allowed to cool to ambient temperature. Theresulting colored fluid was then filtered with a 0.2 μm filter.

TABLE 2 Non-aqueous Food Grade Colored Fluid Formulations SAMPLE ASAMPLE B SAMPLE C Color Blue (Cyan) Magenta Yellow 1,2-propanediol 92.3389.49 89.93 Methylparaben 0.05 0.05 0.05 Propylparaben 0.02 0.02 0.02Glycerine 4.00 6.00 6.00 FD&C Blue 1 1.60 0.008 FD&C Red 3 2.30 FD&C Red40 0.130 FD&C Yellow 5 2.30 Isopropanol 2.00 2.00 2.00 Surface Tension(dynes/cm) 39.6 39.1 38.4 Viscosity (centipoise) 54.2 53.5 58.2 HeatTest SDI 0.96 0.99 0.998 Apparent pH 4.89 8.48 6.86 Absorbance 0.5690.613 0.569 (@ 629 nm) (@ 526 nm) (@ 427 nm) Specific Gravity 1.04931.0638 1.0638

Each of the FD&C dyes listed in Tables 2-4 and 6-8 are available fromSensient Colors, Inc., St. Louis, Mo.

Example 2 Preparation of Low Water Content Food Grade Colored Fluids

This example describes a method for producing low water content foodgrade colored fluids from food grade FD&C dyes, 1,2-propanediol andglycerine. Seven illustrative formulations and colors for theseformulations are shown in Tables 3 and 4. The colored fluids were madeaccording to the procedure described in Example 1 above, with theexception that the water and any sodium hydroxide present were addedduring the initial mixing step.

TABLE 3 Low Water Content Food Grade Colored Fluid Formulations SAMPLE DSAMPLE E SAMPLE F SAMPLE G Color Red Yellow Green Blue 1,2-propanediol41.685 43.933 41.94 41.85 Glycerine 38.00 38.00 38.00 38.00 DI Water16.00 14.00 16.00 16.00 1 N NaOH 0.060 FD&C Blue 1 0.015 0.025 0.80 1.60FD&C Red 3 1.00 0.55 FD&C Red 40 1.30 0.042 FD&C Yellow 5 2.00 1.20Isopropanol 2.00 2.00 2.00 2.00 Surface Tension 44.8 43.8 44.1 45.1(dynes/cm) Viscosity 40.0 46.6 40.3 41.4 (centipoise) Heat Test SDI 0.990.83 0.88 0.90 Apparent pH 7.58 6.89 6.65 6.03 Absorbance 0.824 (@ 525nm) 0.529 (@ 426 nm) 0.675 (@ 629 nm) 0.665 (@ 629 nm) 0.357 (@ 412 nm)Specific Gravity 1.13 — 1.123 1.1263

TABLE 4 Low Water Content Food Grade Colored Fluid Formulations SAMPLE HSAMPLE I SAMPLE J Color Black Black Brown 1,2-propanediol 42.88 43.5542.54 Methylparaben 0.05 0.05 Propylparaben 0.02 0.02 Glycerine 38.0038.00 40.00 DI Water 14.00 14.00 13.00 1 N NaOH 0.05 0.05 FD&C Yellow 60.35 0.28 FD&C Blue 1 0.96 0.77 0.18 FD&C Red 40 1.69 1.35 1.28 FD&CYellow 5 0.93 Isopropanol 2.00 2.00 2.00 Surface Tension 45.0 44.5 44.0(dynes/cm) Viscosity (centipoise) 47.1 47.2 51.9 Heat Test SDI 0.81 0.850.62 Apparent pH 6.74 6.95 6.19 Absorbance 0.790 0.610 0.295 (@ 629 nm)(@ 629 nm) (@ 629 nm) 0.590 0.436 0.717 (@ 504 nm) (@ 504 nm) (@ 494 nm)0.246 0.191 0.689 (@ 409 nm) (@ 409 nm) (@ 426 nm) Specific Gravity1.1259 1.127 1.1287

Example 3 Preparation of Food Grade Colored Fluids from Natural Dyes

This example describes a method for producing food grade colored fluidsfrom food grade natural dyes, 1,2-propanediol and glycerine. Fourillustrative formulations and colors for these formulations are shown inTable 5. The colored fluids were made according to the proceduredescribed in Example 1 above, with the exception that any water presentwas added in the initial mixing step and the natural dyes were added inthe second mixing step, rather than the FD&C dyes.

TABLE 5 Food Grade Colored Fluid Formulations Made From Natural DyesSAMPLE K SAMPLE L SAMPLE M SAMPLE N Color Red Yellow Yellow Blue1,2-propanediol 59.5 39.7 42.0 24.0 Glycerine 6.00 6.0 6.0 4.0 DI Water50.0 50.0 Carminic Acid 32.5 (7.5%) liquid^(a) Gardenia Yellow^(b) 2.0Turmeric Liquid^(c) 50.0 Gardenia Blue^(d) 20.0 Isopropanol 2.00 2.002.00 2.00 Surface Tension 41.7 46.3 37.1 46.4 (dynes/cm) Viscosity(centipoise) 18.4 5.92 38.0 13.1 Apparent pH 7.42 3.96 4.67 5.62Absorbance 0.718 (@ 556 nm) 0.394 (@ 438 nm) 0.368 (@ 425 nm) 0.929 (@596 nm) 0.694 (@ 527 nm) Specific Gravity 1.064 1.054 1.035 1.113 ^(a)Anatural food dye obtained from Sensient Colors, Inc., containing 7.5 wt.% cochineal in propylene glycol. ^(b)A natural food dye obtained fromSensient Colors, Inc. ^(c)A natural food dye obtained from SensientColors, Inc., containing 7.7 wt. % ethyl alcohol, 90.8 wt. % propyleneglycol and 1.5 wt. % oleoresin turmeric which itself contains 48-50 wt.% curcumin with a balance of flavor and gum components. ^(d)A naturalfood dye obtained from Sensient Colors, Inc.

Example 4 Preparation of Low Inorganic Salt Content Food Grade ColoredFluids

This example describes a method for producing low inorganic salt contentfood grade colored fluids from low salt food grade FD&C dyes,1,2-propanediol and glycerine. Three illustrative formulations andcolors for these formulations are shown in Table 6. The colored fluidswere made according to the procedure described in Example 1 above.

TABLE 6 Low Inorganic Salt Content Colored Fluid Formulations SAMPLE OSAMPLE P SAMPLE Q Color Yellow Blue (Cyan) Blue (Blue) 1,2-propanediol91.80 92.33 91.78 Glycerine 4.00 4.00 4.00 Methylparaben 0.05 0.05Propylparaben 0.02 0.02 Low Salt FD&C Blue 1^(e) 1.60 1.60 FD&C Red 30.55 Low Salt FD&C Yellow 5^(f) 2.20 Isopropanol 2.00 2.00 2.00 SurfaceTension (dynes/cm) 39.6 39.2 39.4 Viscosity (centipoise) 53.9 49.5 50.4Heat Test SDI — 0.51 0.82 Apparent pH 7.84 5.53 7.75 Absorbance 0.5930.973 0.677 (@ 428 nm) (@ 629 nm) (@ 629 nm) 0.168 (@ 526 nm) SpecificGravity 1.0505 1.0493 1.0529 ^(e)The formulation for this low salt bluedye is presented in Table 1, above. ^(f)The formulation for this lowsalt yellow dye is presented in Table 1, above.

Example 5 Preparation of Low Viscosity Food Grade Colored Fluids

This example describes a method for producing low viscosity food gradecolored fluids from food grade FD&C dyes, 1,2-propanediol and glycerine.Three illustrative formulations and colors for these formulations areshown in Tables 7 and 8. The colored fluids were prepared as follows.The 1,2-propanediol, glycerine, water and Docusate sodium were mixedtogether at 40° C. for approximately 20 minutes. The FD&C dyes were thenadded while mixing, the heater was turned off, and mixing continued forabout one hour. The mixture was allowed to cool to ambient temperature.The resulting colored fluid was then filtered with a 0.2 μm filter.

TABLE 7 Low Viscosity Food Grade Colored Fluid Formulations SAMPLE RSAMPLE S SAMPLE T Color Cyan Cyan Cyan 1,2-propanediol 50.0 49.3 70.0 DIwater 41.9 33.0 23.9 Glycerine 5.0 14.0 3.0 1% Docusate sodium 1.5 0 1.51.0 N NaOH 0 0.10 0 FD&C Blue 1 1.6 1.6 1.6 Isopropanol 0 2.0 0 SurfaceTension 48.0 44.0 44.4 (dynes/cm) Viscosity 7.62 11.4 14.8 (centipoise)SDI 0.92 Apparent pH 5.51 5.76 5.24 Absorbance — 0.665 (@ 629 nm)Specific Gravity — 1.071

TABLE 8 Low Viscosity Food Grade Colored Fluid Formulations SAMPLE USAMPLE V SAMPLE W Color Magenta Yellow Black 1,2-propanediol 49.60949.23 47.83 Methylparaben 0.05 0.05 0.05 Propylparaben 0.02 0.02 0.02Glycerine 14.0 14.0 14.0 DI Water 32.0 32.5 33.0 FD&C Blue 0.008 0.96FD&C Red 3 2.30 FD&C Red 40 0.013 1.69 FD&C Yellow 5 2.20 FD&C Yellow 60.35 Isopropanol 2.0 2.0 2.0 Surface Tension (dynes/cm) 44.5 44.2 44.6Viscosity (centipoise) 11.5 12.0 11.8 pH 8.43 6.44 7.48 Absorbance 0.6330.547 0.408 (@ 526 nm) (@ 425 nm) (@ 629 nm) Specific Gravity 1.0831.076 1.0818 Heat Test SDI

Example 6 Application of Food Grade Colored Fluids to an EdibleSubstrate

Colored fluids can be printed through commercially available printingequipment employing printheads manufactured by manufacturers of piezoprintheads such as Spectra, Xaar, Hitachi and PicoJet. When jettingSample P, for example, the printhead is set to 60° C. One example of aprinthead which could be used for jetting these fluids is the NovaQjetting assembly 256/80 AQ, manufactured by Spectra. Inks successfullyjet at frequencies including, but not limited to, 1 kHz to 20 kHz. Basedon the printhead design and ink ingredients (formulations) inks may bejettable up to a frequency of 40 kHz. For highest resolution a substrategap of 1 mm may be desirable. Substrates such as cookies, crackers,breads, marshmallows, and other edible items in a wide variety of shapesand thickness may be jetted.

The invention has been described with reference to very specific andillustrative embodiments. However, it should be understood that manyvariations and modifications may be made while remaining within thespirit and scope of the invention.

1. A method of applying an edible colorant to a surface of an ediblesubstrate, comprising ink jet printing onto the surface a food gradecolored fluid comprising a food grade dye, glycerine, at least about 25wt. % 1,2-propanediol, and optionally water; wherein the1,2-propanediol, glycerine and any optional water make up at least about90 wt. % of the colored fluid, and any water present makes up no morethan about 35 wt. % of the colored fluid.
 2. The method of claim 1,wherein the surface is a porous surface.
 3. The method of claim 1,wherein the food grade colored fluid has a viscosity of about 8 to 14cps at a temperature between about 20 and 75° C.
 4. The method of claim1, wherein the food grade colored fluid has a viscosity of about 8 to 14cps at 60° C.
 5. The method of claim 1, wherein the ink jet printingtakes place at a jetting temperature of about 25 to 75° C.
 6. The methodof claim 1, wherein the ink jet printing takes place at a jettingtemperature of about 50 to about 70° C.
 7. The method of claim 1,wherein the ink jet printing takes place using at least onepiezoelectric print head.
 8. The method of claim 1, wherein the ediblesubstrate is selected from the group consisting of crackers, chewinggum, biscuits, cereal, taco shells, granola bars, rice cakes, cookies,pie crusts, waffles, cakes, marshmallows, candies, pasta and breadproducts.
 9. A method of applying an edible colorant to a surface of anedible substrate, the method comprising ink jet printing onto thesurface a food grade colored fluid comprising a food grade dye, a foodgrade glycol, optionally glycerine and optionally water; wherein thefood grade glycol and any optional glycerine and water make up at leastabout 90 wt. % of the colored fluid, and any water present makes up nomore than about 35 wt. % of the colored fluid; and further wherein thecolored fluid has a Brookfield viscosity at 60° C. that changes by nomore than 2 cps over a shear rate range from about 10 to 45 rpm.
 10. Themethod of claim 9, wherein the surface is a porous surface.
 11. Themethod of claim 9, wherein the food grade colored fluid has a viscosityof about 35 to 65 cps at 25° C.
 12. The method of claim 9, wherein theink jet printing takes place at a jetting temperature of about 25 to 75°C.
 13. The method of claim 9, wherein the ink jet printing takes placeusing at least one piezoelectric print head.
 14. The method of claim 9,wherein the edible substrate is selected from the group consisting ofcrackers, chewing gum, biscuits, cereal, taco shells, granola bars, ricecakes, cookies, pie crusts, waffles, cakes, marshmallows, candies, pastaand bread products.
 15. A method of applying an edible colorant to asurface of an edible substrate, the method comprising ink jet printingonto the surface a food grade colored fluid comprising a food grade dyeand at least about 25 wt. % 1,2-propanediol, wherein the food grade dyehas an inorganic salt content of no more than about 0.5 wt. %.
 16. Themethod of claim 15, wherein the surface is a porous surface.
 17. Themethod of claim 15, wherein the food grade colored fluid has a viscosityof about 35 to 65 cps at 25° C.
 18. The method of claim 15, wherein theink jet printing takes place at a jetting temperature of about 25 to 75°C.
 19. The method of claim 15, wherein the ink jet printing takes placeusing at least one piezoelectric print head.
 20. The method of claim 15,wherein the edible substrate is selected from the group consisting ofcrackers, chewing gum, biscuits, cereal, taco shells, granola bars, ricecakes, cookies, pie crusts, waffles, cakes, marshmallows, candies, pastaand bread products.
 21. A method of applying an edible colorant to asurface of an edible substrate, the method comprising ink jet printingonto the surface a food grade colored fluid comprising a food grade dyeand at least about 70 wt. % 1,2-propanediol, glycerine or a mixturethereof, wherein the colored fluid has a viscosity of about 35 to 65 cpsat 25° C.
 22. The method of claim 21, wherein the surface is a poroussurface.
 23. The method of claim 21, wherein the food grade dyecomprises a natural dye.
 24. The method of claim 21, wherein the ink jetprinting takes place at a jetting temperature of about 25 to 75° C. 25.The method of claim 21, wherein the ink jet printing takes place usingat least one piezoelectric print head.
 26. The method of claim 21,wherein the edible substrate is selected from the group consisting ofcrackers, chewing gum, biscuits, cereal, taco shells, granola bars, ricecakes, cookies, pie crusts, waffles, cakes, marshmallows, candies, pastaand bread products.
 27. A method of applying an edible colorant to asurface of an edible substrate, the method comprising ink jet printingonto the surface a food grade colored fluid comprising a food grade dye,at least about 85 wt. % 1,2-propanediol, about 2 to 10 wt. % glycerine,and no more than about 5 wt. % water, wherein the colored fluid has aproperty selected from a viscosity of about 35 to 65 cps at 25° C., asurface tension of about 20 to 60 dynes per cm at 25° C. and acombination thereof.
 28. The method of claim 27, wherein the surface isa porous surface.
 29. The method of claim 27, wherein the food grade dyecomprises a natural dye.
 30. The method of claim 27, wherein the ink jetprinting takes place at a jetting temperature of about 25 to 75° C. 31.The method of claim 27, wherein the ink jet printing takes place usingat least one piezoelectric print head.
 32. The method of claim 27,wherein the edible substrate is selected from the group consisting ofcrackers, chewing gum, biscuits, cereal, taco shells, granola bars, ricecakes, cookies, pie crusts, waffles, cakes, marshmallows, candies, pastaand bread products.
 33. A method of applying an edible colorant to asurface of an edible substrate, the method comprising ink jet printingonto the surface a food grade colored fluid comprising a food grade dye,at least about 90 wt. % 1,2-propanediol, glycerine, or a mixturethereof, and no more than about 5 wt. % water, wherein the colored fluidhas a property selected from a viscosity of about 8 to 14 cps at 60° C.,a surface tension of about 20 to 60 dynes per cm at 25° C., and acombination thereof.
 34. The method of claim 33, wherein the surface isa porous surface.
 35. The method of claim 33, wherein the food grade dyecomprises a natural dye.
 36. The method of claim 33, wherein the ink jetprinting takes place at a jetting temperature of about 25 to 75° C. 37.The method of claim 33, wherein the ink jet printing takes place usingat least one piezoelectric print head.
 38. The method of claim 33,wherein the edible substrate is selected from the group consisting ofcrackers, chewing gum, biscuits, cereal, taco shells, granola bars, ricecakes, cookies, pie crusts, waffles, cakes, marshmallows, candies, pastaand bread products.